QUESTION 1

Tim,

I have a small block Chevy 406 (490 hp & 520 ft/lbs) that I am going to put in a '76 Datsun 260Z. I am going to back-half the car and I have a 9-inch Ford already. I can't decide on which suspension to use, a 4-link or ladder bar set-up. I have thought of using ladder bars with leaf springs since they are less complicated to set up, but I am willing to learn if you know of another set-up that will work better for me. This car is going to be driven on the street, but will spend most of its time at the track. I want this car to hook hard and go straight, so any info you could give me would be greatly appreciated.

Thanks a lot.
Keith Elder

Keith,

I would suggest using the ladder bar system for your car. Both types of suspension will work well but the ladder bar will be much easier to install and tune. I would recommend going to coil over shocks instead of the leaf springs. Coil over are a lot cleaner package when you are finished and they are easy to set and change at the track. There are a lot of ladder bar suspension packages available today that make it a breeze to install. Just do some homework and find out who has the best quality and the most thorough instructions.

Good luck.
Tim

QUESTION 2

I have a '72 Corvette that was back halfed a few years ago. It has a 4-link with a Ford 9-inch rear. The original frame was cut right before the rear fender wells. The 4-link rods are a bit short at 21 inches. Does this matter? I want to step up to a faster class (9-sec. range). What type of frame configuration do you recommend for a fast bracket car like this? Can I use a chrome moly cage with a mild steel tube frame? Can they be mixed? It's a bit tight to get in and out with a regular cage.

Thanks. (You are the greatest!)
Charlie

Charlie,

You can have a 4130 roll cage with a mild steel chassis as long as you weld it with a mild steel rod (70s-2). You should be fine with the four-link configuration you have. The four-link bar length will work great for your car. Make sure that you tie the rear frame rails together all the way to the front of the car and use the cage to bridge the whole thing together.

Corvettes don't have a huge amount of room to deal with, so you have to be very careful and fit the tubing as tight to the body as possible.

Tim

QUESTION 3

I own a 1969 Camaro. Engine is a 509 with aluminum heads, a TH-400 transmission with 4500 stall converter. Rear is a GM 12-bolt with 4.56 gears. I run a multi-leaf spring (3 leafs). The springs are from Landrum springs in Georgia. I don't know the spring rate. The car with driver is 3640 lbs. The car is street driven and sees some track time too. The problem that I am having at the track is that when the car leaves the line it pulls the front tires off the ground and then drops them. The car then begins to bounce up and down as it makes its way to the 60-ft mark. The tires are losing bite. I use Cal-trac bars on my car. They have one turn of preload in them. The rear has a six degree of wedge in it. I have run 2 and 4 degrees too, with no change. The front end is stock. Stock small block springs for A/C. Bushings are stock. Shocks are Koni Spa-1 drag shock. The battery is still in its stock location.

My question is: What do I do to stop the car from bouncing off the line? Do I use a spring with less spring rate in the back? I have tried new slicks. The problem is still there, but not as bad. Any help would be appreciated.

Jack Stiles

Jack,

Are the Koni shocks adjustable? If so, have you tried adjusting them? Is the Cal-trac bar you have like a ladder bar? If it is not, I suggest installing a quality set of ladder bars. I think the problem you are having is that the rear suspension just can't keep the weight of the car transferred smoothly and it is loading and unloading the chassis. There is a lot of tuning capability in the rear shocks so I would start there first.

Tim

It's been a while since we had a chassis Q&A, but we now have veteran chassis builder and Pro Mod racer Tim McAmis to give you the benefit of his years of experience. So keep those questions coming and look for the answers right here in Check Out This Chassis!

 

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